1. Field of the Invention
The present invention relates to methods and apparatus for operating self-propelled construction machines, and more particularly, but not by way of limitation, to methods and apparatus for operating slipform paving machines.
2. Description of the Prior Art
One known arrangement for a self-propelled construction machine includes a generally rectangular machine frame having a swing leg mounted at each corner of the frame and having a crawler track mounted at the free end of each swing leg. The crawler tracks provide the motive force for the construction machine. The mounting of the crawler tracks on the swing legs allows the crawler tracks to be repositioned in a horizontal plane relative to the machine frame for various reasons. For example, a slipform paving machine utilizing such construction may need to spread the forward extending swing legs in order to make room for a paving kit or other equipment supported from the machine frame. Also, it may be desirable during operation of the machine to relocate one or more of the swing legs and its associated crawler track to avoid obstacles. Also, the swing legs allow the crawler tracks to be repositioned for transport of the construction machine.
Various systems have been proposed for repositioning of the swing legs relative to the machine frame for transport of the construction machine.
One system set forth in Swisher U.S. Pat. No. 3,970,405 provides that each track is individually raised off of the ground surface one at a time, and then the swing leg is manually pivoted to the desired orientation where it is fixed in place using turn buckles. The transport position of the Swisher machine is shown in its FIG. 2. Disadvantages of this system include the need to individually raise each track off the ground one at a time, and the need to realign the steering after adjusting the leg orientation.
Another approach is found in Aeschlimann U.S. Pat. No. 6,872,028 in which the swing legs are constructed as parallelogram linkages mounted on a mounting bracket. The entire mounting bracket and parallelogram linkage can be pivoted 90 degrees for transport as shown in FIG. 16 of Aeschlimann.
Another solution is provided in Guntert U.S. Pat. No. 8,459,898. Each crawler track is steerable through a steering angle of 90 degrees relative to its swing leg. As shown in Guntert FIGS. 8A-8E, with the track oriented at 90 degrees to the swing leg, the track is advanced to pivot the swing leg through a pivot angle of 90 degrees to a transport position. Guntert pivots its swing legs one at a time from the paving orientation to the transport orientation, while the machine frame remains in a fixed position on the ground.
None of the techniques for repositioning of the swing legs relative to the machine frame for transport of the construction machine described above provide for the re-orientation of the frame on the ground to align the frame of the paving machine with a transport vehicle. In the prior art such re-orientation is typically done separately prior to the repositioning of the swing legs relative to the machine frame.
Thus there is a continuing need for improvements in the arrangements for the control of the pivoting of swing legs of such automotive construction machines to reorient the swing legs to a transport position.